Airbag apparatus

ABSTRACT

An airbag apparatus includes an airbag. The airbag includes a gas releasing valve having first and second valve body portions each have a flexible portion. The flexible portions are flexible toward a released gas downstream side of inflation gas. An auxiliary joint portion joins the first and second valve body portions to each other and extending, from a position in the vicinity of and on a released gas upstream side of the flexible portion, further toward the released gas upstream side. A flex-resistant portion that extends in the gas releasing direction and is less flexible than the flexible portion is arranged on the auxiliary joint portion of the gas releasing valve or in the vicinity of the auxiliary joint portion.

BACKGROUND OF THE INVENTION

The present invention relates to an airbag apparatus mounted in avehicle to protect an occupant of the vehicle or pedestrians from animpact and, more particularly, to an airbag apparatus having an airbagincluding a vent hole and a gas releasing valve, which selectively opensand closes the vent hole.

Airbag apparatuses are widely known as apparatuses for protectingoccupants of vehicles or pedestrians. An airbag apparatus has an airbag,which is formed by sewing peripheral portions of a pair of fabric sheetstogether, and an inflator arranged in the airbag.

In one such air bag apparatus, such as a side airbag apparatus forprotecting an occupant from an impact from the side, the airbag isincorporated in a seat back of a vehicle together with the inflator.

When an impact is applied to a body side portion of the vehicle from theside, the side airbag apparatus supplies inflation gas from the inflatorinto the airbag. The inflation gas inflates and deploys the airbag, andthe airbag comes out of the seat of the vehicle with a part of theairbag remaining in the seat back. The airbag is inflated and developedforward in the narrow space between the occupant seated on the seat andthe body side portion of the vehicle. When inflated and developed, theairbag is arranged between the occupant and the body side portion, whichprojects into the interior of the vehicle, restrains and protects theoccupant. After the airbag is inflated and developed, the excessiveinflation gas in the airbag is discharged to the outside of the airbagthrough a vent hole formed in the airbag.

As a technique related to such vent holes, Japanese Laid-Open PatentPublication No. 2007-22306, for example, discloses an airbag apparatushaving a gas releasing valve that opens a vent hole according to thepressure in the airbag. The airbag apparatus employs a sheet having anopening formed at the center as a gas releasing valve. The gas releasingvalve has a first sheet portion and a second sheet portion, each ofwhich forms a corresponding half of the sheet with respect to theopening, which is the boundary. The gas releasing valve is arrangedoutside the airbag in such a manner that the opening corresponds to thevent hole. The gas releasing valve is then joined to the airbag alongthe periphery of the vent hole. Further, the first sheet portion and thesecond sheet portion are joined together in such a manner as to closethe opening of the sheet. When the pressure in the airbag becomesgreater than or equal to a predetermined value, the first sheet portionand the second sheet portion of the gas releasing valve are separatedfrom each other, thus exposing the vent hole.

The airbag apparatus maintains the vent hole closed by the gas releasingvalve until the airbag is inflated and the pressure in the airbagreaches the predetermined value. This prevents the inflation gas fromescaping to the outside of the airbag through the vent hole. Thisquickly raises the pressure in the airbag, thus promoting, or in otherwords, increasing the speed of inflation of the airbag. When thepressure in the airbag becomes greater than or equal to thepredetermined value, the first sheet portion and the second sheetportion of the gas releasing valve are disconnected from each other atthe joint portion, in such a manner as to expose the vent hole. Thisdischarges the inflation gas from the vent hole to the outside of theairbag, thus decreasing the pressure in the airbag. As a result, theoccupant is protected from an impact by the airbag having an appropriatelevel of hardness.

In the airbag apparatus described in the aforementioned document, thevent hole is opened by operating the gas releasing valve according tothe pressure in the airbag. However, the vent hole is opened byrupturing the joint portion between the first sheet portion and thesecond sheet portion of the gas releasing valve. Such a method, whichphysically breaks the joint portion, makes it difficult to open the venthole in response to a certain level of pressure in the airbag. In otherwords, it is difficult to suppress variation of the rupture strength ofthe first sheet portion and the second sheet portion of the gasreleasing valve. This varies the timings at which the vent hole isopened. Accordingly, the airbag apparatus must be improved in order tosuppress such variation of the valve opening timings and enhance thestability for opening the gas releasing valve.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide asimply configured gas releasing valve that suppresses variation ofopening timings of a vent hole without depending on a method involvingrupture of a joint portion.

To achieve the foregoing objective and in accordance with one aspect ofthe present invention, an airbag apparatus having an airbag having aninflating portion is provided. The inflating portion of the airbag has apair of gas releasing walls. A vent hole is formed between the gasreleasing walls to discharge inflation gas from the inflating portion.The airbag includes a gas releasing valve having a first valve bodyportion and a second valve body portion that are arranged in thevicinity of the vent hole and overlapped with each other. The gasreleasing valve operates according to a pressure in the airbag toselectively open and close the vent hole. The first valve body portionand the second valve body portion each have an end at a released gasdownstream side on which the inflation gas is discharged. The end ofeach of the first valve body portion and the second valve body portionon the released gas downstream side is joined to corresponding one ofthe gas releasing walls with a downstream end joint portion extending ina direction crossing a releasing direction of the inflation gas. Thefirst and second valve body portions each have a flexible portionarranged in a part in the vicinity of and on a released gas upstreamside of the corresponding downstream end joint portion. The flexibleportions are flexible toward the released gas downstream side of theinflation gas. Each of the first and second valve body portions has afirst side portion and a second side portion on both sides of anextending direction of the downstream end joint portion. The first sideportion of each valve body portion is joined to at least thecorresponding gas releasing wall with a first edge joint portion. A walljoint portion, which joins at least both gas releasing walls to eachother, is arranged on the first edge joint portion or in the vicinity ofthe first edge joint portion. The second side portions of the firstvalve body portion and the second valve body portion are joined to eachother with a second edge joint portion extending in the gas releasingdirection. An auxiliary joint portion is arranged between the first edgejoint portion and the second edge joint portion and in the vicinity ofthe second edge joint portion. The auxiliary joint portion joins thefirst valve body portion and the second valve body portion to each otherand extends, from a position in the vicinity of and on the released gasupstream side of the flexible portion, further toward the released gasupstream side. A flex-resistant portion that extends in the gasreleasing direction and is less flexible than the flexible portion isarranged on the auxiliary joint portion of the gas releasing valve or inthe vicinity of the auxiliary joint portion.

Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a side view showing, together with an occupant, a vehicle seatin which a side airbag apparatus according to one embodiment of thepresent invention is mounted;

FIG. 2 is a plan cross-sectional view showing the vehicle seatillustrated in FIG. 1, the occupant, and a body side portion;

FIG. 3 is a front cross-sectional view showing the vehicle seatillustrated in FIG. 1, the occupant, and the body side portion;

FIG. 4 is a side view showing, together with the occupant, an airbagmodule with an airbag in a flatly developed state;

FIG. 5 is a side view showing an inflator assembly arranged in theairbag illustrated in FIG. 4;

FIG. 6 is a plan view showing the inflator assembly illustrated in FIG.5 as viewed from diagonally above and behind, together with a seatframe, a nut, and the airbag;

FIG. 7 is a developed view showing, together with the inflator assembly,the airbag held in a flatly developed state and a gas releasing valve inthe process of manufacture of the airbag module;

FIG. 8 is an enlarged cross-sectional view showing a part of theinterior of the airbag module when the seat back is uprightsubstantially in a vertical direction, illustrating the gas releasingvalve and the proximity of the gas releasing valve;

FIG. 9 is a cross-sectional view showing a part of the gas releasingvalve at an early stage of inflation of the airbag;

FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 8;

FIG. 11 is a diagram schematically illustrating the gas releasing valvebefore the airbag is inflated;

FIG. 12 is a diagram schematically illustrating the gas releasing valveat the early stage of inflation of the airbag;

FIG. 13 is a diagram schematically illustrating a state of the gasreleasing valve illustrated in FIG. 12 after the gas releasing valve hasbeen further operated;

FIG. 14 is a diagram schematically illustrating a state of the vent holeclosed through operation of the gas releasing valve illustrated in FIG.13 due to a pressure rise in the airbag;

FIG. 15 is a diagram schematically illustrating the vent hole in a statefully closed by the gas releasing valve illustrated in FIG. 14, thusrestricting discharge of inflation gas;

FIG. 16 is a diagram schematically illustrating a flex-resistant portionof the gas releasing valve illustrated in FIG. 14 reversed to open thevent hole;

FIG. 17 is a graph representing the S (stroke)-F (Load) characteristicsof the side airbag apparatus;

FIG. 18 is a cross-sectional view corresponding to FIG. 8, showing apart of a modification of a gas releasing valve having a wall jointportion that is formed at a position different from the position of thefirst edge joint portion;

FIG. 19 is a cross-sectional view showing a part of the gas releasingvalve taken along line 19-19 of FIG. 18;

FIG. 20 is a diagram corresponding to FIG. 8 and showing a part ofanother modification of a gas releasing valve having a flex-resistantportion that is formed at a position different from the position of theauxiliary joint portion; and

FIG. 21 is a cross-sectional view showing a part of the gas releasingvalve taken along line 21-21 of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A side airbag apparatus according to one embodiment of the presentinvention will now be described with reference to FIGS. 1 to 17. In thedescription below, the direction in which the vehicle advances (movesforward) is defined as the forward direction.

As illustrated in FIGS. 1 to 3, a vehicle seat 12 is arranged on theinner side of and in the vicinity of a body side portion 11 of a vehicle10. The body side portion 11 refers to components arranged on both sidesof the widthwise direction of the vehicle 10. For example, the body sideportion 11 corresponding to a front seat includes a front door and acenter pillar (a B pillar). The body side portion 11 corresponding to arear seat includes a rear portion of a side door (a rear door), a rearpillar (a C pillar), a front portion of a wheel well, and a rear quarterpanel.

The vehicle seat 12 includes a seat cushion 13 and a seat back 14, whichextends upright from the rear side of the seat cushion 13 and has a tiltadjustment mechanism (not shown). A storage portion 15 is arranged in aside portion of the seat back 14 located on the vehicle outer side. Anairbag module AM, which is a major part of the side airbag apparatus, isstored in the storage portion 15. The storage portion 15 is locateddiagonally rearward from and in the vicinity of an occupant P who isseated on the vehicle seat 12. The airbag module AM mainly includes aninflator assembly 20 (see FIG. 5) serving as a gas supply source and anairbag 30, which is inflated by inflation gas supplied from the inflatorassembly 20.

The respective components of the airbag module AM will hereafter beexplained. In the present embodiment, the up-down direction and thefront-rear direction of the airbag module AM and its components aredefined with reference to the seat back 14 of the vehicle seat 12. Thatis, the direction in which the seat back 14 is upright is referred to asthe up-down direction, and the direction of the thickness of the seatback 14 is referred to as the front-rear direction. Normally, the seatback 14 is used in a state tilted slightly rearward. Accordingly, theup-down direction is not strictly the vertical direction, butcorresponds to a slightly tilted direction. Similarly, the front-reardirection is not strictly the horizontal direction, but corresponds to aslightly tilted direction.

<Inflator Assembly 20>

FIG. 4 schematically illustrates the airbag module AM with the airbag 30that is flat without inflation gas G (hereinafter, referred to as aflatly developed state), together with the occupant P. FIG. 5illustrates the inflator assembly 20, which is arranged in the airbag 30illustrated in FIG. 4. FIG. 6 illustrates the inflator assembly 20illustrated in FIG. 5 as viewed from diagonally above and behind.

With reference to FIGS. 4 to 6, the inflator assembly 20 has an inflator21 and a retainer 22, which covers the inflator 21 from outside. Theinflator 21 substantially has a columnar shape that is elongatedsubstantially along the up-down direction. A gas generating agent (notshown), which generates the inflation gas G in response to an activationsignal from the outside, is received in the inflator 21. A plurality ofgas holes 23, through which the generated inflation gas G is blastedradially outward, are formed in an upper portion of the inflator 21. Aconnector portion 24 is arranged in a lower end portion of the inflator21. A harness 25 serving as a cable for sending a control signal to theinflator 21 is connected to the connector portion 24.

As the inflator 21, a type that blasts the inflation gas G by rupturinga partition wall of a high-pressure gas cylinder retaining high-pressuregas using low explosive may be employed instead of the aforementionedtype, which employs the gas generating agent.

The retainer 22 functions as a diffuser and fixes the inflator 21,together with the airbag 30, to a seat frame 16 (see FIG. 6) arranged inthe seat back 14. A most part of the retainer 22 is shaped substantiallyas a cylinder that is elongated substantially in the up-down directionby bending a plate such as a metal plate. A window 26, through whichsome of the gas holes 23 of the inflator 21 are exposed from theretainer 22, is formed in an upper front part of the retainer 22. Theinflation gas G is blasted from the gas holes 23 generally toward thefront side of the vehicle 10 through the window 26.

The retainer 22 is fixed to the seat frame 16 by means of a plurality of(in the present embodiment, two) bolts 27 serving as locking members. Inother words, the inflator 21 is fixed indirectly by the bolts 27 withthe retainer 22. Each of the bolts 27 extends in a directionperpendicular to the axis L1 of the inflator 21.

The inflator assembly 20 may formed by an inflator 21 and a retainer 22that are formed as an integral body.

<Airbag 30>

As shown in FIGS. 1 to 3, when the vehicle 10 is hit from the side whilemoving, and an impact is applied to the body side portion 11 from theside (from below as viewed in FIG. 2, and from the left as viewed inFIG. 3), the airbag 30 is inflated and developed by the inflation gas G(see FIGS. 5 and 6) sent from the inflator 21. The airbag 30 then comesout from the storage portion 15 substantially toward the front side ofthe vehicle 10 with a part remaining in the storage portion 15. Theairbag 30 is thus inflated and developed in a gap G1 between the vehicleseat 12 and the body side portion 11. This allows the airbag 30 torestrain the occupant P, thus protecting the occupant P from theaforementioned impact.

FIG. 7 illustrates the airbag 30 in the process of manufacture. As shownin FIGS. 4 and 7, the airbag 30 is formed by a fabric panel 31, which isa single fabric sheet. Specifically, the airbag 30 is formed by foldingthe fabric panel 31 in half along a fold line 32, which is set along themidline of the fabric panel 31, and joining the overlapped portionstogether in a bag-like shape. To distinguish the two overlapped portionsof the airbag 30, a part that is located on the vehicle inner side isreferred to as a fabric portion 33, and a part located on the vehicleouter side is referred to as a fabric portion 34.

In the fabric panel 31, the outlines of the two fabric portions 33, 34are axisymmetrical with each other with respect to the fold line 32. Thefabric portions 33, 34 are each shaped and sized in such a manner that,when the airbag 30 is inflated and developed between the vehicle seat 12and the body side portion 11, the airbag 30 occupies the zonecorresponding to the thorax PT of the occupant P outside and in thevicinity of the occupant P, who is seated on the vehicle seat 12.

In the fabric portion 33, which is located on the vehicle inner side,bolt holes 35 are formed at two positions in the vicinity of the foldline 32, which are spaced apart in the up-down direction.

The fabric portions 33, 34 are joined together along a peripheral jointportion 36, which is arranged along the peripheries of the fabricportions 33, 34. In the present embodiment, the peripheral joint portion36 is formed by sewing a part of the periphery of the fabric portion 33except for the rear end and the upper and lower ends with acorresponding part of the periphery of the fabric portion 34 (usingsewing threads).

In FIGS. 4, 7, 8, 11, 12, 13, 14, 15, 16, 18, and 20, the sewn portionsare represented by two types of lines, which are bold broken lines anddotted lines. The bold broken lines represent the sewing threads on theouter sides (not between the inner sides) of the fabric sheets to besewn (see FIGS. 4 and 7, for example). The dotted lines represent thesewing threads inside the fabric sheets (between the inner sides of thefabric sheets) to be sewn (see FIGS. 8 and 11, for example). In otherwords, the drawings representing the sewing threads by the dotted linesillustrate a cross section along the sewn portions.

The space between the two fabric portions 33, 34 and surrounded by theperipheral joint portion 36 forms an inflating portion 37. The inflatingportion 37 is inflated by the inflation gas G outside and in thevicinity of the thorax PT of the occupant P, thus protecting the thoraxPT of the occupant P from an impact. In the present embodiment, theinterior of the airbag 30 is not divided and the airbag 30 includes onlythe inflating portion 37.

Alternatively, the airbag 30 may be formed by overlapping a pair ofindependent fabric panels with each other. In this case, the fabricpanel located on the vehicle inner side is the fabric portion 33, andthe other fabric panel, which is located on the vehicle outer side isthe fabric portion 34. The fabric portions 33, 34 are joined together ina bag-like shape.

Further, the peripheral joint portion 36 may be formed by means otherthan the aforementioned means using the sewing threads, which is, forexample, adhesion using an adhesive. A first downstream end jointportion 53, a second downstream end joint portion 54, a first edge jointportion 55, a wall joint portion 57, a flex-resistant portion 59, and anauxiliary joint portion 61, which will be explained later, will beformed by any suitable means in similar manners.

<Attachment of Inflator Assembly 20 to Airbag 30>

As illustrated in FIG. 4, the inflator assembly 20 is arranged in alower portion of the airbag 30 and at the front side and in the vicinityof the fold line 32, while being inclined downward toward the front. Thetwo bolts 27 of the retainer 22 are passed through the correspondingbolt holes 35 (see FIG. 7) of the fabric portion 33, which is located onthe vehicle inner side. This maintains the inflator assembly 20 in astate positioned with respect to the airbag 30. A lower rear end of theairbag 30 is airtightly fastened to a lower part of the inflatorassembly 20 by means of an annular fastener 28.

A gas releasing hole, which is a vent hole 38, is formed in the airbag30 to discharge the inflation gas G so as to adjust the pressure in theinflating portion 37. In the present embodiment, the vent hole 38 islocated in an upper end portion of the airbag 30 and at the front sideand in the vicinity of the fold line 32. The inflation gas G is thusdischarged substantially upward from the inflating portion 37 of theairbag 30 through the vent hole 38. The direction in which the inflationgas G flows in this state is defined as a gas releasing direction. Aside closer to the center of the inflating portion 37 with respect tothe vent hole 38 is defined as a released gas upstream side. A sidespaced from the center of the inflating portion 37 with respect to thevent hole 38 (a side corresponding to the outside of the airbag 30) isdefined as a released gas downstream side.

As illustrated in FIGS. 8 to 10, the vent hole 38 is formed by a part ofan upper part of each one of the fabric portions 33, 34, which areoverlapped with each other, and located at a position at which theperipheral joint portion 36 is not arranged. In the fabric portion 33 onthe vehicle inner side, the portion forming the vent hole 38 and thevicinity of the vent hole 38 is defined as a first gas releasing wall41, for the sake of distinction from other portions. Also, in the fabricportion 34 located on the vehicle outer side, the portion forming thevent hole 38 and the vicinity of the vent hole 38 is defined as a secondgas releasing wall 42, for the sake of distinction from other portions.The gas releasing walls 41, 42 are held in flat shapes when the airbag30 is not inflated.

Further, in the present embodiment, a gas releasing valve 50 is providedto selectively open and close the vent hole 38 according to the pressurein the inflating portion 37. The gas releasing valve 50 will hereafterbe explained.

<Gas Releasing Valve 50>

With reference to FIGS. 7 to 10, the gas releasing valve 50 is formed bya single fabric sheet 48. The fabric sheet 48 is arranged on the fabricportions 33, 34 of the fabric panel 31 including the fold line 32 of thefabric panel 31. With a fold line 49, which is set along the midline ofthe fabric sheet 48, coinciding with the fold line 32 of the fabricpanel 31, the fabric sheet 48 is folded in half, together with thefabric panel 31, along the fold lines 32, 49. In this manner, the fabricsheet 48 is folded flatly. To distinguish the two overlapped portions ofthe fabric sheet 48 from each other, a part that is located on thevehicle inner side is defined as a first valve body portion 51, and apart that is located on the vehicle outer side is defined as a secondvalve body portion 52.

The end of the first valve body portion 51 on the released gasdownstream side is joined to the first gas releasing wall 41 of theairbag 30, which is located on the vehicle inner side, through the firstdownstream end joint portion 53. The first downstream end joint portion53 extends substantially along the front-rear direction, which crossesthe releasing direction of the inflation gas G. The end of the secondvalve body portion 52, which is located on the vehicle outer side, onthe released gas downstream side is joined to the second gas releasingwall 42 of the airbag 30, which is located on the vehicle outer side,through the second downstream end joint portion 54. The seconddownstream end joint portion 54 extends substantially along thefront-rear direction, which crosses the gas releasing direction of theinflation gas G. In the gas releasing valve 50, the first valve bodyportion 51 located on the vehicle inner side and the second valve bodyportion 52 located on the vehicle outer side are not joined together atthe ends located on the released gas downstream side.

As illustrated in FIGS. 8 to 10, a front part of each one of the firstvalve body portion 51 and the second valve body portion 52, which servesas a first side portion of the valve body portion 51, 52 in thedirection in which the associated downstream end joint portion 53, 54extends, is joined to at least the corresponding gas releasing wall 41,42 with the first edge joint portion 55. In the present embodiment, thefront part of each valve body portion 51, 52 is joined to thecorresponding gas releasing wall 41, 42 with the first edge jointportion 55. The first edge joint portion 55 is formed by sewing thefront parts of the valve body portions 51, 52 and the gas releasingwalls 41, 42 together (integrally). The first edge joint portion 55extends from the ends of the valve body portions 51, 52 on the releasedgas downstream side toward the released gas upstream side, thus reachingthe ends of the valve body portions 51, 52 on the released gas upstreamside. The end of the first edge joint portion 55 on the released gasdownstream side crosses the peripheral joint portion 36. The first edgejoint portion 55 functions also as the wall joint portion 57. The walljoint portion 57 is arranged on the first edge joint portion 55 or inthe vicinity of the first edge joint portion 55 and joins at least thetwo gas releasing walls 41, 42 together.

A flexible portion 58 is arranged in a part of the first valve bodyportion 51 in the vicinity of and on the released gas upstream side ofthe first downstream end joint portion 53. Specifically, the zonebetween the first downstream end joint portion 53 and the positionspaced from the first downstream end joint portion 53 by the length L2toward the released gas upstream side (encompassed by the single-dottedchain lines in FIG. 8) is the flexible portion 58, which is soft andeasily flexed toward the released gas downstream side when receiving thepressure of the inflation gas G. Similarly, the corresponding part ofthe second valve body portion 52 in the vicinity of and on the releasedgas upstream side of the second downstream end joint portion 54 is theflexible portion 58, which is soft and easily flexed toward the releasedgas downstream side when receiving the pressure of the inflation gas G.

The rear parts of the first valve body portion 51 and the second valvebody portion 52, which serve as second side portions in the extendingdirection of the downstream end joint portions 53, 54, are joinedtogether with the second edge joint portion 56 extending toward thereleased gas upstream side. In the present embodiment, the first valvebody portion 51 located on the vehicle inner side and the second valvebody portion 52 located on the vehicle outer side are formed by foldingthe single fabric sheet 48 in half along the fold line 49. Accordingly,the folded portion of the fabric sheet 48 (in the proximity of the foldline 49) corresponds to the second edge joint portion 56.

A flex-resistant portion 59 is arranged in a rear part of each valvebody portion 51, 52 in the extending direction of the downstream endjoint portion 53, 54, and more accurately, the zone spaced slightlyforward from the fold line 49 of the fabric sheet 48. In the rear partof each valve body portion 51, 52, the flex-resistant portion 59 extendsfrom the position on the released gas upstream side and in the vicinityof the associated flexible portion 58 further toward the released gasupstream side. Specifically, the position on the released gas upstreamside and in the vicinity of each flexible portion 58 is the positionspaced from the associated downstream end joint portion 53, 54 by acertain distance (the length L2), with the flexible portion 58 arrangedbetween this position and the downstream end joint portion 53, 54. Theflex-resistant portions 59 are formed by sewing the valve body portions51, 52 together along one or more rows (in the present embodiment, tworows) using sewing threads. The flex-resistant portions 59 are harder(has more rigidity) and less flexible than the flexible portions 58 andother joint portions of the gas releasing valve 50 (which are thedownstream end joint portions 53, 54, the first edge joint portion 55,the second edge joint portion 56, and the wall joint portion 57).

Each of the flex-resistant portions 59 functions also as an auxiliaryjoint portion 61. Each auxiliary joint portion 61 joins the first valvebody portion 51 to the second valve body portion 52 at a positionbetween the first edge joint portion 55 and the second edge jointportion 56 of the valve body portions 51, 52 and in front of and in thevicinity of the second edge joint portion 56. The auxiliary jointportion 61 extends toward the released gas upstream side from theposition spaced from the downstream end joint portion 53, 54 toward thereleased gas upstream side, with the flexible portion 58 located betweenthe downstream end joint portion 53, 54 and the auxiliary joint portion61.

Since the first edge joint portion 55 (the wall joint portion 57) andeach flex-resistant portion 59 (each auxiliary joint portion 61) extendlinearly toward the released gas upstream side, the first edge jointportion 55 (the wall joint portion 57) and the flex-resistant portion 59(the auxiliary joint portion 61) extend parallel with each other.Accordingly, the interval (the flow passage area of the inflation gas G)between the first edge joint portion 55 (the wall joint portion 57) andeach flex-resistant portion 59 (each auxiliary joint portion 61) isuniform along the longitudinal directions of the first edge jointportion 55 and the flex-resistant portion 59 (along the gas releasingdirection).

Each flex-resistant portion 59 restricts separation between the ends ofthe gas releasing walls 41, 42 on the released gas downstream side andseparation between the ends of the valve body portions 51, 52 on thereleased gas downstream side (with respect to the corresponding ends).The extent of such restriction becomes higher as a downstream end 59E ofthe flex-resistant portion 59 becomes closer to the downstream end jointportions 53, 54 (as the length L2 becomes smaller) or as theflex-resistant portion 59 becomes closer to the wall joint portion 57.Accordingly, the downstream end 59E of the flex-resistant portion 59 isarranged at such a position (height) that the downstream end 59E isprevented from greatly hampering the separation of the downstream endsof the gas releasing walls 41, 42 and the valve body portions 51, 52.

As illustrated in FIG. 11, in the gas releasing valve 50 having theabove-described configuration, the flex-resistant portion 59 (theauxiliary joint portion 61) is located at a position spaced forward fromthe fold line 49 (the second edge joint portion 56) of the fabric sheet48. Accordingly, in the flexible portion 58, the interval D1 between thefold line 49 (the second edge joint portion 56) and the wall jointportion 57 (the first edge joint portion 55) is set to a value greaterthan the interval D2 between the flex-resistant portion 59 (theauxiliary joint portion 61) and the wall joint portion 57 (the firstedge joint portion 55). This indicates that, when the inflation gas Gflows between the valve body portions 51, 52 and thus inflates the gasreleasing valve 50, the zone between the flex-resistant portion 59 (theauxiliary joint portion 61) and the wall joint portion 57 (the firstedge joint portion 55) is inflated in a cylindrical shape having adiameter smaller than the diameter of the flexible portion 58, which isthe zone between the second edge joint portion 56 and the wall jointportion 57 (the first edge joint portion 55).

With reference to FIG. 8, each flex-resistant portion 59 has a lengthL3. The interval between a position B of the wall joint portion 57 (thefirst edge joint portion 55), at which the interval between the walljoint portion 57 and the flex-resistant portion 59 is minimum, and arear end C of each downstream end joint portion 53, 54 is defined as theinterval D3. In the present embodiment, the length L3 and the intervalD3 are set in such a manner that the expression L3>D3 is satisfied. Ashas been described, the flex-resistant portion 59 (the auxiliary jointportion 61) and the first edge joint portion 55 (the wall joint portion57) extend parallel with each other. Accordingly, the part of the firstedge joint portion 55 (the wall joint portion 57) at the front side ofthe flex-resistant portion 59 (the auxiliary joint portion 61)corresponds to the position B, at which the interval between the firstedge joint portion 55 (the wall joint portion 57) and the flex-resistantportion 59 (the auxiliary joint portion 61) is minimum uniformly alongthe gas releasing direction.

The end of the first valve body portion 51 on the released gas upstreamside and the end of the second valve body portion 52 on the released gasupstream side are not joined together at a position of each valve bodyportion 51, 52 on the released gas upstream side. As has been described,the end of the first valve body portion 51 on the released gasdownstream side is joined to the first gas releasing wall 41 (the fabricportion 33 located on the vehicle inner side) and the end of the secondvalve body portion 52 on the released gas downstream side is joined tothe second gas releasing wall 42 (the fabric portion 34 located on thevehicle outer side). However, the ends of the first valve body portion51 and the second valve body portion 52 on the released gas downstreamside are not joined together. This allows the gas releasing valve 50 toinflate in a tubular shape having two ends that are open on the releasedgas upstream side and the released gas downstream side.

As illustrated in FIG. 9, the first valve body portion 51 of the gasreleasing valve 50, which is located on the vehicle inner side, isjoined to the fabric portion 33 located on the vehicle inner side withthe first downstream end joint portion 53. This prohibits the inflationgas G from flowing between the first valve body portion 51 and thefabric portion 33, from the inside of the inflating portion 37 towardthe outside or from the outside of the inflating portion 37 toward theinside. Similarly, the second valve body portion 52 of the gas releasingvalve 50, which is located on the vehicle outer side, is joined to thefabric portion 34 located on the vehicle outer side with the seconddownstream end joint portion 54. This prohibits the inflation gas G fromflowing between the second valve body portion 52 and the fabric portion34, from the inside of the inflating portion 37 toward the outside orfrom the outside of the inflating portion 37 toward the inside. Theinflation gas G is permitted to flow from the inside of the inflatingportion 37 toward the outside only through the flow path between thevalve body portions 51, 52 of the gas releasing valve 50.

As illustrated in FIG. 6, the airbag module AM is shaped in asmall-sized and compact form (hereinafter, referred to as a storageform) both in the front-rear direction and the up-down direction byfolding the airbag 30 that is held in the flatly developed state (seeFIG. 4). In this manner, the airbag module AM becomes suitable for beingstored in the storage portion 15 of the seat back 14, which has alimited (narrow) space.

When held in the storage form, the airbag module AM is fixed to the seatframe 16 with the two bolts 27. Specifically, the two bolts 27 passedthrough the corresponding bolt holes 35 of the airbag 30 are insertedthrough the seat frame 16, with nuts 17 fastened to the bolts 27.

The retainer 22 may be fixed to the vehicle 10 (such as the seat frame16) by means of any suitable components other than the bolts 27.

The side airbag apparatus has an impact sensor 71 and a controller 72,apart from the above-described airbag module AM, as illustrated inFIG. 1. The impact sensor 71 is formed by an acceleration sensor andattached to the body side portion 11 of the vehicle 10 in order todetect an impact applied to the body side portion 11 from the side. Thecontroller 72 controls operation of the inflator 21 based on a detectionsignal of the impact sensor 71.

The side airbag apparatus of the present embodiment is configured in theabove-described manner. Next, a main operating mode of the side airbagapparatus will be explained with reference to FIGS. 12 to 16. FIGS. 12to 16 schematically represent change of the form of the gas releasingvalve 50 as the time elapses depending on whether supply of theinflation gas G is allowed or stopped. In the drawings, illustration ofdetails is omitted or simplified.

In the side airbag apparatus, the airbag 30 is maintained in the storageform and stored continuously in the storage portion 15, together withthe inflator assembly 20, unless the vehicle 10 receives an impact fromthe side. In this state, the valve body portions 51, 52 of the gasreleasing valve 50 are held continuously in a state overlapped with eachother (see FIG. 11).

When the vehicle 10 is moving and an impact greater than a predeterminedlevel is applied to the body side portion 11, the impact is detected bythe impact sensor 71. The controller 72 then outputs an activationsignal for activating the inflator 21 to the inflator 21 in response tothe detection signal of the impact sensor 71. With reference to FIGS. 5and 6, in response to the activation signal, the gas generating agent ofthe inflator 21 generates high temperature and pressure inflation gas G.The inflation gas G is thus blasted through the gas holes 23 indirections perpendicular to the axis L1 of the inflator 21 (radialdirections). In this state, rear ones of the gas holes 23 are closed bythe retainer 22 and front ones of the gas holes 23 are exposed from thewindow 26. This blasts the inflation gas G from the front ones of thegas holes 23 substantially toward the front side of the vehicle 10through the window 26. The front side of the vehicle 10 herein includesnot only the front side but also an upper front side and a lower frontside.

When the inflating portion 37 is in a non-inflated state and theinflation gas G is supplied to the inflating portion 37, some of theinflation gas G flows in the gap between the first valve body portion 51and the second valve body portion 52 of the gas releasing valve 50 andproceeds toward the outside of the inflating portion 37 (see FIG. 9).When the inflation gas G flows in the gap between the first valve bodyportion 51 and the second valve body portion 52, the force inflating thevalve body portions 51, 52 in a cylindrical shape is produced in thevalve body portions 51, 52, as illustrated in FIGS. 9 and 12.

Specifically, the end of the first valve body portion 51 on the releasedgas downstream side is joined to the first gas releasing wall 41 and theend of the second valve body portion 52 on the released gas downstreamside is joined to the second gas releasing wall 42. Further, the parts(the front parts) of the valve body portions 51, 52 at one side of theextending direction of the downstream end joint portions 53, 54 arejoined to the gas releasing walls 41, 42 integrally with the first edgejoint portion 55 (the wall joint portion 57). Also, the parts (the rearparts) of the valve body portions 51, 52 on the other side of theextending direction of the downstream end joint portions 53, 54 arejoined to each other with the flex-resistant portion 59 (the auxiliaryjoint portion 61) and the second edge joint portion 56. Accordingly, thevalve body portions 51, 52 are inflated in the cylindrical shape.

However, when the valve body portions 51, 52 are to be inflated in thecylindrical shape, the diameter (the circumferential length) of eachflexible portion 58 is different from the diameter of the portionlocated on the released gas upstream side of the flexible portion 58. Ashas been described, in the gas releasing valve 50, each flex-resistantportion 59 (the auxiliary joint portion 61) is arranged at the positionspaced forward from the second edge joint portion 56 (the fold line 49)of the fabric sheet 48. Accordingly, in the flexible portion 58, theinterval D1 between the second edge joint portion 56 (the fold line 49)and the wall joint portion 57 (the first edge joint portion 55) is setto a value greater than the interval D2 between the flex-resistantportion 59 (the auxiliary joint portion 61) and the wall joint portion57 (the first edge joint portion 55) (see FIG. 11). As a result, theparts of the valve body portions 51, 52 located on the released gasupstream side of the flexible portion 58 are to be inflated each in acylindrical shape having a diameter (a circumferential length) smallerthan that of the flexible portion 58.

However, as has been described, the parts (the front parts) of the valvebody portions 51, 52 at one side of the extending direction of thedownstream end joint portions 53, 54 are joined to the gas releasingwalls 41, 42. Contrastingly, the parts (the rear parts) of the valvebody portions 51, 52 on the other side of the extending direction of thedownstream end joint portions 53, 54 are joined only to each other withthe flex-resistant portion 59 (the auxiliary joint portion 61) withoutbeing joined to the gas releasing walls 41, 42. In other words, theparts (the front parts) of the valve body portions 51, 52 at one side ofthe extending direction of the downstream end joint portions 53, 54 areimmovable with respect to the gas releasing walls 41, 42. However, theparts (the rear parts) of the valve body portions 51, 52 on the otherside of the extending direction of the downstream end joint portions 53,54 are movable with respect to the gas releasing walls 41, 42. Further,in the valve body portions 51, 52, the flex-resistant portions 59 arehard and not flexible but the flexible portions 58 are soft andflexible.

Accordingly, as has been described, the flexible portion 58 of eachvalve body portion 51, 52 is inflated in a cylindrical shape having arelatively great diameter (circumferential length) and the part of thevalve body portion 51, 52 is inflated in a cylindrical shape having arelatively small diameter (circumferential length). The flexibleportions 58 are thus moved toward the released gas downstream side andbent. This moves the parts of the valve body portions 51, 52 located onthe released gas upstream side of the flexible portions 58 as indicatedby arrow A in FIG. 12. In other words, the parts of the valve bodyportions 51, 52 at the released gas upstream side are each moved aboutthe portion in the vicinity of the downstream end 59E of theflex-resistant portion 59 (encompassed by frame F of the single-dottedchain line in FIG. 13), which is the support point, toward thedownstream end joint portions 53, 54 (upward) and toward the wall jointportion 57 (the first edge joint portion 55) (forward). This inclineseach flex-resistant portion 59 in such a manner that a part closer tothe released gas upstream side is located more forward. Further, in theparts of the valve body portions 51, 52 located on the released gasupstream side of the flexible portions 58, the flex-resistant portions59 are not flexible but the other portions are flexible. Accordingly, asthe part of each valve body portion 51, 52 at the released gas upstreamside is moved in the above-described directions, crumples are formedeasily in the portion between the wall joint portion 57 (the first edgejoint portion 55) and the flex-resistant portion 59 (the auxiliary jointportion 61), which are flexible.

As has been described, the inflation gas G flows in the gap between thefirst valve body portion 51 and the second valve body portion 52 andproceeds toward the outside of the airbag 30. This suppresses a pressurerise of the inflation gas G in the gap between the valve body portions51, 52.

As the inflation gas G is generated, the airbag 30 starts to inflate.Since the airbag 30 is inflated despite the suppressed pressure rise ofthe inflation gas G in the gap between the valve body portions 51, 52,the interval between each valve body portion 51, 52 and thecorresponding gas releasing wall 41, 42 is increased (see FIG. 9). Theends of the valve body portions 51, 52 at the released gas downstreamside are joined to the corresponding gas releasing walls 41, 42 with theassociated downstream end joint portions 53, 54, each of which extendsin the direction crossing the gas releasing direction of the inflationgas G. This prevents the inflation gas G from flowing toward thereleased gas downstream side of the downstream end joint portions 53,54. Accordingly, the inflation gas G is accumulated in the space betweenthe first valve body portion 51 and the first gas releasing wall 41 andthe space between the second valve body portion 52 and the second gasreleasing wall 42.

When the pressure of the inflation gas G in the space between each valvebody portion 51, 52 and the corresponding gas releasing wall 41, 42exceeds the pressure of the inflation gas G in the space between thevalve body portions 51, 52, the gas releasing valve 50 operates in themanner described below. Specifically, the flexible portions 58, whichare moved toward the released gas downstream side and flexed due to thedifference in the diameters (the circumferential lengths), receive thepressure of the inflation gas G and thus become pressed toward thereleased gas downstream side. This further presses the flexible portions58 of the valve body portions 51, 52 further upward as indicated byarrow H in FIG. 13. Correspondingly, the part of each valve body portion51, 52 on the released gas upstream side of the flexible portion 58 ismoved further toward the downstream end joint portion 53, 54 (furtherupward) and further toward the wall joint portion 57 (further forward).

In this state, each flex-resistant portion 59 is also moved upward andapproaches the downstream end joint portion 53, 54. Then, whilemaintaining its shape, the flex-resistant portion 59 is bent about theend (the downstream end 59E) of the flex-resistant portion 59 that islocated close to the downstream end joint portion 53, 54, which is thesupport point, toward the downstream end joint portion 53, 54 (upward)and toward the wall joint portion 57 (forward). In this state, like theflexible portions 58, the parts of the valve body portions 51, 52located on the released gas upstream side of the flexible portions 58,except for the flex-resistant portions 59, also receive the pressure ofthe inflation gas G in the inflating portion 37, which is directedtoward the released gas downstream side. After having received thepressure, as indicated by arrow I in FIG. 14, the portions are bentdiagonally upward and forward in such a manner that the portions arepressed into the space between the valve body portions 51, 52. Thisdecreases the space between the valve body portions 51, 52, which is theflow passage area of the inflation gas G.

In the present embodiment, the length L3 of each flex-resistant portion59 is greater than the interval D3 (L3>D3), as has been described.Accordingly, when the flex-resistant portion 59 is bent diagonallyupward in the above-described manner, the flex-resistant portion 59contacts the wall joint portion 57 (the first edge joint portion 55),with reference to FIG. 15. The wall joint portion 57 (the first edgejoint portion 55) restricts bending of each flex-resistant portion 59further toward the downstream end joint portion 53, 54 (further upward)and further toward the wall joint portion 57 (further forward). In thisstate, the gas releasing valve 50 substantially closes the vent hole 38.This prevents the inflation gas G in the airbag 30 (the inflatingportion 37) from flowing toward the outside of the airbag 30 (theinflating portion 37) via the gap between the valve body portions 51,52.

Particularly, in the present embodiment, the inflation gas G in theairbag 30 (the inflating portion 37) flows to the outside of the airbag30 only via the gas releasing valve 50. The inflation gas G in theairbag 30 (the inflating portion 37) is prevented from escaping to theoutside of the airbag 30 (the inflating portion 37) without passingthrough the gas releasing valve 50. This prevents the rising speed ofthe pressure in the airbag 30 (the inflating portion 37) from droppingdue to the aforementioned escape of the inflation gas G.

As the inflating portion 37 is inflated in the above-described manner,the airbag 30 is unfolded and developed in the order opposite to theorder by which the airbag 30 has been folded.

The airbag 30 then comes out of the seat back 14 with the rear partremaining in the storage portion 15 of the seat back 14. As theinflation gas G is supplied continuously to the airbag 30, the airbag 30is unfolded and developed between the body side portion 11 and thethorax PT of the occupant P seated on the vehicle seat 12 and toward thefront side of the vehicle 10 as illustrated in FIGS. 2 and 3. The airbag30 is thus arranged between the occupant P and the body side portion 11,which projects toward the interior of the vehicle 10. The airbag 30 thuspresses the thorax PT of the occupant P inward in the widthwisedirection of the vehicle and restrains the thorax PT of the occupant P.In this manner, the airbag 30 absorbs the impact applied to the thoraxPT of the occupant P through the body side portion 11 from the side,thus protecting the thorax PT of the occupant P.

The vent hole 38 is maintained closed by the gas releasing valve 50continuously until the pressure of the inflation gas G in the airbag 30(the inflating portion 37) exceeds a predetermined value α. The value αis the upper limit of the range of pressure required for protecting andrestraining the thorax PT of the occupant P.

As the inflation gas G is continuously supplied to the interior of theinflating portion 37 with the vent hole 38 held in a closed state or theoccupant P is restrained by the airbag 30 in the inflated state, thepressure in the inflating portion 37 increases. When the pressure in theinflating portion 37 reaches the value α, each flex-resistant portion59, which has been held in contact with the wall joint portion 57 (thefirst edge joint portion 55) and thus stopped, moves beyond the walljoint portion 57 (the first edge joint portion 55). The flex-resistantportion 59 is then pushed out to the outside of the inflating portion 37through the gap between the valve body portions 51, 52. Correspondingly,the parts of the valve body portions 51, 52 on the released gas upstreamside of the flexible portions 58, following movement of theflex-resistant portions 59, move beyond the wall joint portion 57 andturn over (become reversed). That is, a part of the gas releasing valve50 is pushed out to the outside of the inflating portion 37 through thevent hole 38. Through such pressing (reversal), the vent hole 38, whichhas been closed by the valve body portions 51, 52, becomes open,allowing the inflation gas G to flow from the inflating portion 37 tothe outside of the inflating portion 37 via the vent hole 38. Thisdecreases the pressure in the inflating portion 37.

In this state, variation of the timings at which the vent hole 38 isopened by the gas releasing valve 50 is suppressed compared to theconventional technique in which the vent hole is opened by rupturing thejoint portion. Specifically, unlike the apparatus of the conventionaltechnique that physically ruptures the joint portion, the gas releasingvalve 50 does not include a part that is physically ruptured in order toopen the vent hole 38, which is a part exhibiting a varied rupturestrength when ruptured. That is, the gas releasing valve 50 operatesaccording to the pressure in the inflating portion 37, without beinginfluenced by the varied rupture strength. This suppresses variation ofthe timings at which the vent hole 38 is opened by the gas releasingvalve 50.

Although the main operating mode of the gas releasing valve 50 has beendescribed above, other operating modes different from theabove-described mode may be employed. In one such mode, the gasreleasing valve 50 operates in the same manner as the above-describedmain mode until the gas releasing valve 50 reaches the state illustratedin FIG. 12. Specifically, the flexible portion 58 of each valve bodyportion 51, 52 and the part of the valve body portion 51, 52 on thereleased gas upstream side of the flexible portion 58 are inflated incylindrical shapes having different diameters (circumferential lengths).The flexible portions 58 are thus moved toward the released gasdownstream side. Then, the associated flex-resistant portion 59 (theassociated auxiliary joint portion 61) is moved toward the downstreamend joint portion 53, 54 (upward) and toward the wall joint portion 57(the first edge joint portion 55) (forward).

Afterwards, the parts of the valve body portions 51, 52 on the releasedgas upstream side of the flexible portions 58 are brought closer to eachother by the pressure of the inflation gas G. These parts of the valvebody portions 51, 52 are thus overlapped with each other (held in tightcontact with each other). In this overlapped (tightly contacting) state,the overlapped parts of the valve body portions 51, 52 become crushedtoward the released gas downstream side, thus closing the vent hole 38.When the pressure in the airbag 30 (the inflating portion 37) reachesthe predetermined value a, the gas releasing valve 50 operates in thesame manner as the above-described main mode.

The present embodiment, which has been described in detail, has theadvantages described below.

(1) In the gas releasing valve 50, the ends of the two valve bodyportions 51, 52 on the released gas downstream side are joined to thecorresponding gas releasing walls 41, 42 with the downstream end jointportions 53, 54. In each of the valve body portions 51, 52, the flexibleportion 58 is arranged in the part of the valve body portion 51, 52 onthe released gas upstream side and in the vicinity of the downstream endjoint portion 53, 54. The part (the front part) of each valve bodyportion 51, 52 at one side of the extending direction of the downstreamend joint portion 53, 54 is joined to at least the corresponding gasreleasing wall 41, 42 with the first edge joint portion 55. The firstedge joint portion 55 functions as the wall joint portion 57, whichjoins at least the two gas releasing walls 41, 42 together. The parts(the rear parts) of the valve body portions 51, 52 on the other side ofthe extending direction of the downstream end joint portions 53, 54 arejoined to each other with the second edge joint portion 56, whichextends toward the released gas upstream side. Each auxiliary jointportion 61 is arranged between the first edge joint portion 55 and thesecond edge joint portion 56 and in the vicinity of the second edgejoint portion 56. The auxiliary joint portion 61 joins the valve bodyportions 51, 52 to each other, and extends from the position on thereleased gas upstream side and in the vicinity of the flexible portion58 further toward the released gas upstream side; The auxiliary jointportion 61 functions also as the flex-resistant portion 59, whichextends toward the released gas upstream side and is less flexible thanthe flexible portion 58.

Accordingly, the gas releasing valve 50 is reliably operated in such amanner that, when the pressure in the airbag 30 (the inflating portion37) is less than the value a, the vent hole 38 is closed and that, oncethe pressure in the airbag 30 (the inflating portion 37) reaches thevalue a, the vent hole 38 becomes open. Further, unlike the apparatus ofthe conventional technique in which the vent hole is opened by rupturingthe joint portion, variation of the timings at which the vent hole 38becomes open is suppressed. Accordingly, the gas releasing valve 50,which operates stably, is provided with a simple configuration. Also, itis unnecessary to provide independent means for driving the gasreleasing valve 50 so as to selectively open and close the gas releasingvalve 50 using the pressure of the inflation gas G.

(2) The length L3 of the flex-resistant portion 59 is greater than theinterval D3 between the position B of the wall joint portion 57 and theend C of each downstream end joint portion 53, 54 in the vicinity of theflex-resistant portion 59. Accordingly, unless the pressure in theairbag 30 (the inflating portion 37) reaches the value α, the flexibleportions 58 and the portions on the released gas downstream side of thedownstream end joint portions 53, 54 are prevented from moving beyondthe wall joint portion 57 and becoming reversed. The passage between thevalve body portions 51, 52 is thus reliably maintained in a closedstate.

(3) If each flex-resistant portion 59 is formed of hard material, it isnot easy to change the flexibility of the flex-resistant portion 59.However, in the present embodiment, the flex-resistant portion 59 isformed simply by sewing the valve body portions 51, 52, which are formedof the originally flexible material (the fabric sheet 48), using sewingthreads. This facilitates formation of each flex-resistant portion 59,which is configured simply and less flexible than the flexible portion58. It is also easy to change the type of the sewing threads or thenumber of the employed sewing threads. This facilitates adjustment ofthe flexibility of the flex-resistant portion 59 in order to set orchange the timing at which the flex-resistant portion 59 is deformed andreversed.

(4) The first edge joint portion 55 and the wall joint portion 57 areformed by sewing the first and second valve body portions 51, 52 and thegas releasing walls 41, 42 together (integrally) using sewing threads.Accordingly, compared to a case in which the first edge joint portion 55and the wall joint portion 57 are formed separately, the first edgejoint portion 55 and the wall joint portion 57 are formed easily andquickly.

(5) The airbag 30 is used as a side airbag apparatus that is inflated bythe inflation gas G, which is supplied in response to an impact from theside of the vehicle 10, and developed between the body side portion 11and the thorax PT of the occupant P seated on the vehicle seat 12 andtoward the front side of the vehicle 10. Accordingly, by preventing thepressure in the airbag 30 (the inflating portion 37) from increasingexcessively with respect to the predetermined value α through operationof the gas releasing valve 50, the airbag 30 (the inflating portion 37)is allowed to gently protect the thorax PT of the occupant P, which hasparticularly low resistance to shock in the side of the body of theoccupant P, from the impact.

(6) Compared to a side airbag apparatus in which the airbag 30 has onlythe vent hole 38 but not the gas releasing valve 50, the side airbagapparatus of the present embodiment has the following advantage.

FIG. 17 represents the relationship between the movement amount (thestroke S) of the airbag 30 at the time when the inflation gas G issupplied to the airbag 30 and the airbag 30 is inflated and moved towardthe occupant P and the load F applied to the occupant P. There is apositive correlation between the load F and the pressure in the airbag(the inflating portion 37).

In a side airbag apparatus having only the vent hole 38 but not the gasreleasing valve 50 (see the comparative example of FIG. 17), theinflation gas G starts to escape to the outside of the airbag 30 throughthe vent hole 38 at an early stage of inflation of the airbag 30. Thisprolongs the time needed for increasing the load F to the value (therequired value) necessary for protecting the occupant P, causing a delayof the timing at which the load F reaches the require valued and theoccupant P is restrained and protected.

In contrast, in the airbag apparatus having both of the vent hole 38 andthe gas releasing valve 50 (see the example of the present invention ofFIG. 17), the inflation gas G escapes through the vent hole 38 only foran instant after the airbag 30 (the inflating portion 37) starts toinflate. However, the vent hole 38 is closed by the gas releasing valve50 immediately after this instant. This shortens the time needed for theload F to reach the required value, thus advancing the timing at whichthe load F reaches the required value and the occupant P is restrainedand protected. When the pressure in the airbag 30 (the inflating portion37) becomes greater than or equal to the predetermined value, the gasreleasing valve 50 becomes open and discharges the inflation gas G. Thismaintains the load F at the required value.

If it is assumed that the airbags 30 of both apparatuses carry out equalamounts of work, the case without the gas releasing valve 50 (see thecomparative example) has the characteristic that, after having increasedgradually, the load F exceeds the required value at a later stage ofinflation of the airbag 30, thus reaching the maximum value.Contrastingly, the case with the gas releasing valve 50 (see the exampleof the invention) has the characteristic that the load F reaches therequired value at an early stage of the inflation of the airbag 30 andis maintained substantially constant afterward, which is preferable torestrain and protect the occupant P. Specifically, in this case, theload F has a relatively small maximum value so that the thorax PT of theoccupant P is prevented from receiving an excessively great load.

The present invention may be embodied in the other forms describedbelow.

<Modification to Inflator Assembly 20>

The inflator 21 may be attached directly to the seat back 14 withoutemploying the retainer 22.

The retainer 22 may be changed to an inner tube formed by a fabric sheetand shaped like a tube. Such modification may be carried out only whenit is assumed that the inner tube is prevented from being greatlydamaged by the heat and the pressure of the inflation gas G sent fromthe inflator 21.

Specifically, the modification is permitted when, for example, theinflator 21 is a type that blasts the inflation gas G at a comparativelylow temperature, such as a hybrid type inflator retaining the inflationgas G. Specifically, compared to the pyrotechnic inflator that generatesthe inflation gas G using the gas generating agent through a heatgenerating chemical reaction, the inflation gas G blasted by the hybridtype inflator is low in temperature.

The above-described modification may be carried out even for thepyrotechnic inflator if the inner tube is formed by a coated fabricsheet having a coating layer for improving the heat resistance.

In the airbag apparatus, the inflator assembly 20 may be arrangedoutside the airbag 30. In this case, the inflator 21 and the airbag 30may be connected to each other with a pipe. The inflation gas G, whichis blasted from the inflator 21, is thus supplied to the airbag 30through the pipe.

<Modification to Airbag 30>

The present invention may be used in an airbag apparatus having anairbag 30 with a plurality of inflating portions 37. In this case, theinflating portions 37 may be independent from one another or eachadjacent pair of the inflating portions 37 may communicate with eachother. At lease one of the inflating portions 37 has a vent hole 38 anda gas releasing valve 50.

<Modification to Gas Releasing Valve 50>

The hardness (the rigidity) or the length L3 of each flex-resistantportion 59 may be changed. This adjusts the pressure in the inflatingportion 37 at the time when the flex-resistant portion 59 moves beyondthe wall joint portion 57 and reverses the valve body portions 51, 52.

As means for changing the hardness (the rigidity) of each flex-resistantportion 59 that is formed by sewing, the stitch length (the pitch), thetype, or the size of the sewing threads may be changed. Alternatively,the number of the employed sewing threads may be increased or decreased.

For example, as the size of the sewing threads or the number of thesewing threads becomes greater, the hardness (the rigidity) of theflex-resistant portion 59 becomes greater and the pressure in theinflating portion 37 at the time when the flex-resistant portion 59reverses the valve body portions 51, 52 becomes higher.

If the flex-resistant portion 59 is formed by adhesion, the type or theamount of application (the thickness) of the adhesive may be changed asthe means for changing the hardness (the rigidity) of eachflex-resistant portion 59. For example, as the amount of applicationbecomes greater, the hardness (the rigidity) of the flex-resistantportion 59 becomes greater and the pressure in the inflating portion 37at the time when the flex-resistant portion 59 reverses the valve bodyportions 51, 52 becomes higher.

The vent hole 38 and the gas releasing valve 50 may be arranged atpositions in the airbag 30 that are different from the correspondingpositions of the above-described embodiment.

As illustrated in FIGS. 18 and 19, the first edge joint portions 55 andthe wall joint portion 57 may be arranged at different positions in theairbag 30. That is, the first edge joint portions 55 may be located atany suitable positions as long as the part (the front part) of each ofthe first and second valve body portions 51, 52 at one side of theextending direction of the downstream end joint portion 53, 54 is joinedto at least the corresponding gas releasing wall 41, 42. FIG. 19represents an example in which the first edge joint portion 55 locatedon the vehicle inner side joins the first valve body portion 51 only tothe first gas releasing wall 41 and the first edge joint portion 55located on the vehicle outer side joins the second valve body portion 52only to the second gas releasing wall 42.

The wall joint portion 57 may be arranged at any suitable position aslong as the wall joint portion 57 is in the vicinity of the first edgejoint portion 55 and joins at least the two gas releasing walls 41, 42to each other.

Even in this case, in which the first edge joint portions 55 and thewall joint portion 57 are arranged at the different positions, the sameadvantages as the advantages of the above-described embodiment areensured.

Although the wall joint portion 57 is formed independently from theperipheral joint portion 36 in FIG. 18, the wall joint portion 57 may beformed as a part of the peripheral joint portion 36. For example, a part(a left portion as viewed in FIG. 18) of the peripheral joint portion 36may be curved in a V shape or a U shape. In this case, a left half ofthe V-shaped or U-shaped portion functions also as the wall jointportion 57.

As illustrated in FIGS. 20 and 21, the flex-resistant portion 59 and theauxiliary joint portion 61 may be arranged at different positions ineach of the valve body portions 51, 52. That is, the auxiliary jointportion 61 may be arranged at any suitable position as long as it islocated between the first edge joint portion 55 and the second edgejoint portion 56 and in the vicinity of the second edge joint portion56, joins the valve body portions 51, 52 to each other, and extends fromthe position on the released gas upstream side and in the vicinity ofthe flexible portion 58 further toward the released gas upstream side.The flex-resistant portion 59 may be arranged at any suitable positionas long as it is located on or in the vicinity of the auxiliary jointportion 61 of the gas releasing valve 50, extends toward the releasedgas upstream side, and is less flexible than the flexible portion 58.Even in this case, in which each flex-resistant portion 59 is arrangedat the different position, the same advantages as the advantages of theabove-described embodiment are ensured.

As illustrated in FIGS. 20 and 21, the gas releasing valve 50 may beformed by overlapping a pair of independent fabric sheets. Specifically,the fabric sheet located on the vehicle inner side corresponds to thefirst valve body portion 51 and the fabric sheet located on the vehicleouter side corresponds to the second valve body portion 52. The twovalve body portions 51, 52 are joined together in a tubular shape. Inthis case, the parts (the rear parts) of the valve body portions 51, 52on the other side of the extending direction of the downstream end jointportions 53, 54 are joined to each other with the second edge jointportion 56. In this regard, the modification illustrated in FIGS. 20 and21 is different from the above-described embodiment in which the singlefabric sheet is folded in half and the folded portion (in the proximityof the fold line 49) is defined as the second edge joint portion 56.

Although each flex-resistant portion 59 (each auxiliary joint portion61) of the gas releasing valve 50 is arranged parallel with the foldline 32 of the airbag 30 in the above-described embodiment, theflex-resistant portion 59 may extend in a direction crossing the foldline 32.

The first edge joint portion 55 (the wall joint portion 57) may benonparallel to the flex-resistant portion 59 (the auxiliary jointportion 61). In this case, the first edge joint portion 55 (the walljoint portion 57) may be linear or bent or curved.

On condition that each flex-resistant portion 59 is on or in thevicinity of the auxiliary joint portion 61 of the gas releasing valve50, extends toward the released gas upstream side, and is less flexiblethan the flexible portion 58, the flex-resistant portion 59 may beformed using any suitable material other than sewing threads. Forexample, as illustrated in FIGS. 20 and 21, a rod-like member formed ofsynthetic resin or metal may be employed as the flex-resistant portion59.

The end of each valve body portion 51, 52 on the released gas upstreamside may be either inclined as illustrated in FIG. 8 or non-inclined.

As long as the downstream end joint portions 53, 54 extend in thedirections crossing the releasing direction of the inflation gas G fromthe vent hole 38, the downstream end joint portions 53, 54 do notnecessarily have to extend in directions substantially perpendicular tothe gas releasing direction, unlike the above-described embodiment.

<Modification to Storage Position of Airbag Module AM>

When the airbag apparatus is embodied as a side airbag apparatus as inthe above-described embodiment, the storage portion 15 may be arrangedin a part of the body side portion 11 that is in the vicinity of theoccupant P seated on the vehicle seat 12 and located on the vehicleouter side, instead of in the seat back 14.

<Other Modifications>

When the airbag apparatus is embodied as a side airbag apparatus as inthe above-described embodiment, the body part of the occupant Prestrained and protected by the airbag 30 may be parts different fromthe thorax PT, such as the lumbar region, the abdomen, the shoulder, orany combination thereof.

The present invention may be used in airbag apparatus of types differentfrom the side airbag apparatus, such as a head protecting airbagapparatus, a rear impact airbag apparatus, a forward slide preventingairbag apparatus, a pedestrian protecting airbag apparatus, or a kneeprotecting airbag apparatus.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. An airbag apparatus having an airbag having an inflating portion, theinflating portion of the airbag having a pair of gas releasing walls, avent hole being formed between the gas releasing walls to dischargeinflation gas from the inflating portion, the airbag including a gasreleasing valve having a first valve body portion and a second valvebody portion that are arranged in the vicinity of the vent hole andoverlapped with each other, the gas releasing valve operating accordingto a pressure in the airbag to selectively open and close the vent hole,wherein the first valve body portion and the second valve body portioneach have an end at a released gas downstream side on which theinflation gas is discharged, the end of each of the first valve bodyportion and the second valve body portion on the released gas downstreamside being joined to corresponding one of the gas releasing walls with adownstream end joint portion extending in a direction crossing areleasing direction of the inflation gas, wherein the first and secondvalve body portions each have a flexible portion arranged in a part inthe vicinity of and on a released gas upstream side of the correspondingdownstream end joint portion, the flexible portions being flexibletoward the released gas downstream side of the inflation gas, whereineach of the first and second valve body portions has a first sideportion and a second side portion on both sides of an extendingdirection of the downstream end joint portion, the first side portion ofeach valve body portion being joined to at least the corresponding gasreleasing wall with a first edge joint portion, wherein a wall jointportion, which joins at least both gas releasing walls to each other, isarranged on the first edge joint portion or in the vicinity of the firstedge joint portion, wherein the second side portions of the first valvebody portion and the second valve body portion are joined to each otherwith a second edge joint portion extending in the gas releasingdirection, wherein an auxiliary joint portion is arranged between thefirst edge joint portion and the second edge joint portion and in thevicinity of the second edge joint portion, the auxiliary joint portionjoining the first valve body portion and the second valve body portionto each other and extending, from a position in the vicinity of and onthe released gas upstream side of the flexible portion, further towardthe released gas upstream side, and wherein a flex-resistant portionthat extends in the gas releasing direction and is less flexible thanthe flexible portion is arranged on the auxiliary joint portion of thegas releasing valve or in the vicinity of the auxiliary joint portion.2. The airbag apparatus according to claim 1, wherein the downstream endjoint portion has an end on the side corresponding to the second sideportion, the length of the flex-resistant portion being set to a valuegreater than the distance from the position at which the intervalbetween the wall joint portion and the flex-resistant portion is minimumto the end of the downstream end joint portion.
 3. The airbag apparatusaccording to claim 1, wherein the flex-resistant portion is formed bysewing the first valve body portion and the second valve body portiontogether using a sewing thread.
 4. The airbag apparatus according toclaim 1, wherein the first edge joint portion and the wall joint portionare formed by sewing the first valve body portion, the second valve bodyportion, and both gas releasing walls together using a sewing thread. 5.The airbag apparatus according to claim 1, wherein the airbag apparatusis a side airbag apparatus mounted in a vehicle having a body sideportion and a vehicle seat, the airbag being inflated by the inflationgas supplied in response to an impact applied to the vehicle from theside and developed between the body side portion of the vehicle and anoccupant seated on the vehicle seat and toward the front side of thevehicle.
 6. The airbag apparatus according to claim 1, wherein the venthole is closed by the first valve body portion and the second valve bodyportion through movement of the flex-resistant portion toward the firstside portion caused by supply of the inflation gas, and wherein, whenthe pressure in the airbag becomes greater than or equal to apredetermined value, a part of the gas releasing valve is pushed out ofthe inflating portion through the vent hole, thus opening the vent hole.7. The airbag apparatus according to claim 1, wherein the gas releasingvalve is formed by folding a single sheet in half in a manner inflatablein a tubular shape through supply of the inflation gas.